The architecture of MTC has been studied in 3GPP (3rd Generation Partnership Project). For example, NPLs 1 and 2 disclose typical MTC-IWF (MTC Inter-Working Function) and SCS. Moreover, NPL 3 discloses that an MTC device can communicate with one or more SCSs.
Note that the MTC device is a UE equipped for MTC and subscribed to MTC service, which will be sometimes referred to as “MTC UE” or “UE” in the following description.